ARTICLE - INVERTEBRATE ZOOLOGY THEN AND NOW

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Invertebrate Zoology – Then and Now

Like thousands of life science enthusiasts before and after me I began college studies of invertebrate zoology with a large, 10.5 inch by 7.5 inch, hardcover book called “Invertebrate Zoology” by Robert D. Barnes, Ph.D. Mine was the 1974 issue and was by then the 3^rd edition of Dr. Barnes classic work. Right up until his death in 1993, Dr. Barnes was at work on the 6^th edition of his passion. His principle associate was Dr. Edward E. Ruppert whose name graces the cover of the 1994 edition. By the time of the release of the 7^th edition in 2003, Dr. Ruppert had been joined by Richard S. Fox, although the name of the great Dr. Barnes remained on the text.

Some extraordinary changes have obviously taken place along the way. The 3^rd edition of Invertebrate Zoology listed 29 different phyla of invertebrates. By 1994 that number had expanded to 34 phyla. Now, thanks advances in molecular biology and an emphasis on evolutionary origins in place of morphological similarities the number of invertebrate phyla is reduced to 24 despite the fact that the number of known species has exploded. Ironically, the latest edition is more in agreement with Dr. Barnes’ original classification.

Readers are cautioned about this number, however. Sources vary and scientific arguments abound in this arena. Internet research on the topic is confusing to say the least. What is presented here is based strictly on the work of Barnes, Ruppert, and Fox. Whatever the true number is and whoever the student chooses as his or her final authority one thing is abundantly clear – Invertebrate Zoology is an utterly fascinating subject!

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Invertebrate Zoology

Barnes 3^rd Edition (1974)

Invertebrate Zoology

Rupert/Barnes 7^th Ed (2003)

Remarks

PHYLUM

PHYLUM

Protozoa

Protozoa

Unicellular, eukaryotic organisms (have a cell nuclei); exhibit animal like characteristics such as mobility

METAZOA – Multicellular animals; the majority of animal species are metazoans

Sponges

Porifera

Sponges; primitive multi cellular, sessile animals; primarily marine

Placozoans – discovered on the walls of an aquarium in the 1880s these little creatures (about .5 mm) have never been viewed in a natural habitat

Microscopic in size and may be the simplest animal on earth; only two species discovered to date

EUMETAZOA –subkingdom of animals that includes all but the sponges

Display the presence of tissues and organs that develop from germ layers

Cnidarians

Cnidaria – about 10,000 species; named for the cnidocytes – stinging cells

Hydras, jellyfish, anemones, corals

Ctenophores

Ctenophora

Sea walnuts, comb jellies

BILATERIA – The remainder of the invertebrates listed. All display, in general, a physiology in which the left and right half of their bodies are mirror images. Notable exceptions are the sponges and cnidarians

Bodies develop from 3 different germ layers: endoderm, mesoderm, ectoderm

Flatworms (Platyhelminthes)

Platyhelminthes

Flatworms

Orthonectida

Simple, microscopic parasites of marine invertebrates

Dicyemida

Cephalopod parasites

Nemerteans (Rhynchocoela)

Nemertera

Ribbon worms or proboscis worms; unsegmented marine inverts

Pseudocoelomates

·         Gastrotricha

Mollusca

Clams, oysters, squids, octopods, snails, slugs, nudubranchs; the second largest invertebrate phylum

·         Rotifera

Annelida

Segmented worms such as earthworms and leeches, and many others such as marine species like “feather dusters

·         Kinoryncha

Echiura

“Spoonworms,” inhabit burrows in mud or sand; rock and coral crevices; about 140 species

·         Nematoda

Sipuncula

Marine animals sometimes call “Peanut Worms;” about 320 species animals; predators and parasites

·         Nematomorpha

Onychophora

“Velvet Worms” segmented, caterpillar like; only animal phylum with no marie species

·         Acanthocephala

Tardigrada

“Water Bears” Also famous for their ability to withstand extraordinary temperature and pressure conditions

·         Gnathostomulida

Annelids

Mollusks

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Arthropods

ARTHROPOD PHYLUM - The single largest phylum of any animal; over 750 thousand species – three times the combined number of all other animal species! This phylum is so large that the groups listed below are treated as sub-phylums

Have an exoskeleton and jointed appendages

·         Trilobites (extinct)

·         Trilobitomophora

Extinct

·         Chelicerates

·         Chelicerata

Horseshoe crabs, scorpions, spiders, and mites

·         Crustaceans

·         Crustacea

Copepods, barnacles, shrimp, lobsters, and crabs

·         Insects

·         Hexapoda These are the insects, but now include three other groups formerly classified as insects; the single largest group of animals on earth

750,000 species – and growing!

·         Onychophorans

·         Myriapoda

Centipedes, millipedes,

·         Protostomes

Cycloneuraliasp

A phylum of cuticle building animals that include, among other species the nematodes

Lophophorates

Gnathifera

Wormlike animals, including the “Thorny Headed Worm”

·         Phoronida

Kamptozoa

Small, sessile filter feeders that attach to a substrate with a stalk; sometimes are attached to sponges

·         Bryozoa

Cycliophora – the most recently discovered invertebrate phylum

Three species? Parasite of lobsters

·         Entoprocta

Lophophorata

Distinguished by a feeding organ lophorata - ciliated tentacles

·         Brachiopoda

Chaetognatha

Predatory marine worms often called arrow worms

DEUTEROSOMIA – sub taxon of the bilateria; distinguished by an embryonic development ins which the first opeing becomes the anus (in protostomes it becomes the mouth)

Also referred to as a “superphylum”

·         Echinodermata – 7,000 known species

Sea stars, sand dollars, brittle stars, sea urchins, sea cucumbers, sea lilies, crinoids

Chordata - Most chordates are vertebrates, but these two sub phylum lack a backbone.

Echinoderms

·         Urochordata

“Sea Squirts”

Lesser Deuterostomes

·         Cephalochordata

Resemble fish, but live in marine sand; 28 species

·         Hemichordata

·         Chordates

·         Chaetognatha

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Invertebrate Zoology Barnes 3^rd Edition (1974)	Invertebrate Zoology Rupert/Barnes 7^th Ed (2003)	Remarks
PHYLUM	PHYLUM
Protozoa	Protozoa	Unicellular, eukaryotic organisms (have a cell nuclei); exhibit animal like characteristics such as mobility
	METAZOA – Multicellular animals; the majority of animal species are metazoans
Sponges	Porifera	Sponges; primitive multi cellular, sessile animals; primarily marine
	Placozoans – discovered on the walls of an aquarium in the 1880s these little creatures (about .5 mm) have never been viewed in a natural habitat	Microscopic in size and may be the simplest animal on earth; only two species discovered to date
	EUMETAZOA –subkingdom of animals that includes all but the sponges	Display the presence of tissues and organs that develop from germ layers
Cnidarians	Cnidaria – about 10,000 species; named for the cnidocytes – stinging cells	Hydras, jellyfish, anemones, corals
Ctenophores	Ctenophora	Sea walnuts, comb jellies
	BILATERIA – The remainder of the invertebrates listed. All display, in general, a physiology in which the left and right half of their bodies are mirror images. Notable exceptions are the sponges and cnidarians	Bodies develop from 3 different germ layers: endoderm, mesoderm, ectoderm
Flatworms (Platyhelminthes)	Platyhelminthes	Flatworms
	Orthonectida	Simple, microscopic parasites of marine invertebrates
	Dicyemida	Cephalopod parasites
Nemerteans (Rhynchocoela)	Nemertera	Ribbon worms or proboscis worms; unsegmented marine inverts
Pseudocoelomates
· Gastrotricha	Mollusca	Clams, oysters, squids, octopods, snails, slugs, nudubranchs; the second largest invertebrate phylum
· Rotifera	Annelida	Segmented worms such as earthworms and leeches, and many others such as marine species like “feather dusters
· Kinoryncha	Echiura	“Spoonworms,” inhabit burrows in mud or sand; rock and coral crevices; about 140 species
· Nematoda	Sipuncula	Marine animals sometimes call “Peanut Worms;” about 320 species animals; predators and parasites
· Nematomorpha	Onychophora	“Velvet Worms” segmented, caterpillar like; only animal phylum with no marie species
· Acanthocephala	Tardigrada	“Water Bears” Also famous for their ability to withstand extraordinary temperature and pressure conditions
· Gnathostomulida
Annelids
Mollusks

Arthropods	ARTHROPOD PHYLUM - The single largest phylum of any animal; over 750 thousand species – three times the combined number of all other animal species! This phylum is so large that the groups listed below are treated as sub-phylums	Have an exoskeleton and jointed appendages
· Trilobites (extinct)	· Trilobitomophora	Extinct
· Chelicerates	· Chelicerata	Horseshoe crabs, scorpions, spiders, and mites
· Crustaceans	· Crustacea	Copepods, barnacles, shrimp, lobsters, and crabs
· Insects	· Hexapoda These are the insects, but now include three other groups formerly classified as insects; the single largest group of animals on earth	750,000 species – and growing!
· Onychophorans	· Myriapoda	Centipedes, millipedes,
· Protostomes	Cycloneuraliasp	A phylum of cuticle building animals that include, among other species the nematodes
Lophophorates	Gnathifera	Wormlike animals, including the “Thorny Headed Worm”
· Phoronida	Kamptozoa	Small, sessile filter feeders that attach to a substrate with a stalk; sometimes are attached to sponges
· Bryozoa	Cycliophora – the most recently discovered invertebrate phylum	Three species? Parasite of lobsters
· Entoprocta	Lophophorata	*Distinguished by a feeding organ lophorata* - ciliated tentacles**
· Brachiopoda	Chaetognatha	Predatory marine worms often called arrow worms
	DEUTEROSOMIA – sub taxon of the bilateria; distinguished by an embryonic development ins which the first opeing becomes the anus (in protostomes it becomes the mouth)	Also referred to as a “superphylum”
	· Echinodermata – 7,000 known species	Sea stars, sand dollars, brittle stars, sea urchins, sea cucumbers, sea lilies, crinoids
	Chordata - Most chordates are vertebrates, but these two sub phylum lack a backbone.
Echinoderms	· Urochordata	“Sea Squirts”
Lesser Deuterostomes	· Cephalochordata	Resemble fish, but live in marine sand; 28 species
· Hemichordata
· Chordates
· Chaetognatha